Aquatic-aerial multimodal vehicle is a new concept aircraft that can freely shuttle between water and air. Some of the natural organisms provide the inspiration to realize this multi-locomotion. Most of current prototypes use rigid link mechanisms or hinges to morph the structure thus to adapt to the aquatic-aerial environment, which is commonly complicated and bulky. In this paper, we present a novel prototype with pneumatically-driven soft fins and arms that can fold and spread just like the flying squid. The fins and arms can augment the lift force during flying by spreading and reduce drag force during swimming by folding. The performance of the morphable structures was investigated in wind and water tunnel. The results explain the tradeoff strategies of multimodal-locomotion between water and air, and verify the feasibility of the novel aquatic-aerial vehicle with soft morphable structures.